Element for sealing two parts that can be rotated in relation to one another

ABSTRACT

The invention relates to an element ( 10 ) for scaling two part ( 2, 3 ) that can be rotated in relation to one another Said element comprises at least one first sealing ring ( 11 ) consisting of a permanently elastic material, which is fixed to one of the two rotatable parts and comprises at least one sealing lip ( 21 ) and at least one second sealing ring ( 12 ), which is fixed to the other rotatable part and comprises a strip ( 19 ) consisting of another material that runs along its periphery. At least one sealing lip of the first sealing ring lies against said strip.

This invention relates to an element for sealing two parts that can berotated in relation to one another, with at least one sealing ringconsisting of a permanently elastic material that is fixed to one of thetwo parts that can be rotated in relation to one another, and at leastone sealing lip.

Commercial seals generally consist of a ring consisting of an elasticmaterial that is fastened to one of the two parts that can be rotated inrelation to one another and that has a sealing lip that is tightlypressed against a surface of the other of the two parts that can berotated in relation to one another. For this sealing lip not to wear outprematurely, the contact surface should be as smooth as possible. Amachined and/or polished surface area of the relevant rotating part isordinarily used for this, which may also be protected against corrosionby a grease film. However, this arrangement has drawbacks:

In large bearings, in particular in plant construction, for example inthe case of a pitch bearing of a wind energy system, but also in muchmedical equipment, the relevant rotating part is often so large that itis uneconomical to use stainless steel for this. The use of ordinarysteel that rusts, on the other hand, leads to relatively rapid corrosionfrom the weathering of exposed bearings, since a protective grease filmis quickly washed away by rain. Especially in coastal regions (windenergy systems) or even on the high seas (ships), the air is also verycorrosive because of the salt water. However, as soon as corrosion setsin, the seal is damaged by the roughened surface it causes, and isfinally destroyed.

In other uses, and in the medical technology sector, no grease film oremergence of grease is permissible, so that here also there is nocorrosion protection, and without using a variety of stainless steelthat substantially increases the cost of the equipment in question,corrosion would be unavoidable.

Many bearings can also be serviced only at great expense, so that itwould be desirable for such applications to have available a specialsealing element that does not have to be serviced even in systems with alife expectation of 20 years.

The above considerations result in the problem behind the invention, ofproviding a seal that operates without wear even under rough or evencorrosive environmental conditions and/or without a protective greasefilm for as long a time as possible.

This problem is solved with a seal of this type by at least one secondsealing ring that is fixed to the other of the parts that can be rotatedin relation to one another, and that carries a strip made of anothermaterial that contacts the at least one sealing lip of the first sealingring and that runs along its periphery.

The second sealing ring serves only as the carrier for the strip thatserves as the contact surface for the opposite sealing lip, and cantherefore be matched optimally to this task with regard to the choice ofits material. For example, it can have higher elasticity than thesealing strip to compensate for tolerances of the components. Theassembly and fastening of the sealing strip are considerablyfacilitated, which is important also with regard to a continuous stripsurface. The sealing strip can also be relatively thin, for example 0.5to 2 mm thick, and because of its small weight a high-value, low-wearmaterial can be used for it.

It has proved to be desirable for the material of the second sealingring to have a higher specific electrical resistance p than the materialof the strip it carries. The second sealing ring is preferably made ofan electrically insulating material, for example of a material with aspecific electrical resistance p of more than 10³ Ωm, particularly ofmore than 10⁶ Ωm. Therefore, it sees to it that the strip pursuant tothe invention together with the relevant rotating part does notconstitute a local chemical voltaic cell.

Special benefits are obtained by manufacturing the first and secondsealing rings from the same material. The invention prefers for this avulcanized, i.e. crosslinked, material, for example vulcanized rubber,because this is not only elastic but is permanently elastic as aconsequence of the molecules crosslinked with one another, in contrastto uncrosslinked rubber. Therefore, the result is that thepost-vulcanization that gradually reduces the elasticity existinginitially in uncrosslinked rubber is largely or even completelyeliminated.

Other benefits are available by manufacturing the strip of metal,especially a noble metal or a refined metal, for example stainlesssteel. Because of its relatively great hardness, metal is relativelywear resistant. The development of material-destroying local voltaiccells can be avoided by the insulated fastening to the second sealingring as the carrier. Finally, noble or refined metal is not subject toany corrosion.

It is a great advantage for the material of the strip to have a lowercoefficient of friction μthan the second sealing ring itself. Thisspares the sealing lip even with no grease film, which likewise has abeneficial effect on the achievable service life. The capability ofreducing the coefficient of friction μ exists if the surface area of thestrip serving as the contact surface for a sealing lip of the firstsealing ring is smoothed or polished.

The sliding of the sealing lip along the strip pursuant to the inventionwith as little friction as possible is also supported if the surfacearea of the strip serving as the contact surface for a sealing lip ofthe first sealing ring follows somewhat a surface of rotation,especially a cylindrical envelope surface. This distributes the pressureof the sealing lip uniformly on the entire circumference, and there areno points with elevated wear.

Inasmuch as the strip is closed in a ring, on the one hand, it in turnis given the rotational symmetry necessary to minimize wear of thesealing lip running along it, and on the other hand an annular structureis advantageous for fastening the strip to the second sealing ring. Anannular structure, i.e. a structure that is doubly coherent, can beachieved by welding or cementing the two end faces of the strip,preferably abutting blunt ends, optionally followed by smoothing orpolishing the joint, particularly the weld bead or cement point. Thestrip ends can be joined before or after assembly with the relevantsealing ring, as needed; however, the invention prefers to join thestrip ends before assembly with the relevant sealing ring, or beforeinstalling the seal.

A constant cross section of the strip along its entire periphery servesthe same purpose, namely optimal rotational symmetry. The inventionprefers a somewhat rectangular cross section with the sealing lipfinding an optimal contact surface on one of the wider circumferentialsurfaces of such a strip, while the thickness perpendicular to thissurface can be as small as possible to impart some flexibility to thestrip.

With a view to automatic fastening of the strip, it is recommended tofasten it, using the second sealing ring, to a preferably somewhatcylindrical envelope surface of the relevant rotating part, wherefastening is achieved solely because of geometric characteristics, sothat the use of adhesive is unnecessary.

Especially suitable for this is a convex domed outer envelope surface ofthe relevant rotating part around which the strip pursuant to theinvention can be wrapped like a belt and can thereby have an optimalgrip.

Since the tiniest points of contact between a metallic strip pursuant tothe invention and a likewise metallic rotating part can lead to a localvoltaic cell, the encircling strip should be fixed on the second sealingring in such a way that no contact at all exists with either of the twoparts that can be rotated in relation to one another.

To avoid migration of the strip pursuant to the invention, it can beheld in an encircling trough-like recess in the second sealing ring.

If the depth of the trough in the second sealing ring that holds thestrip pursuant to the invention is less than the correspondingcross-sectional height, i.e. the thickness, of the strip laid in it,then the surface area of the ring pursuant to the invention serving asthe actual contact surface for the sealing lip of the other rotatingpart rises above the delimiting surface areas of the second sealingring. Even if there is a small clearance between the parts that can berotated in relation to one another, then permanent contact between thesealing lip on the first sealing ring with the second sealing ring isthus precluded, and so is damage to these parts caused by friction.

Pressure forces exerted by the sealing lip on the strip pursuant to theinvention—perhaps together with fastening forces produced by the annularstrip itself—act on the bottom surface of a trough in the second sealingring holding the strip. To be able to be passed on from there to therelevant rotating part, the bottom of the trough in the second sealingring holding the encircling strip should run somewhat parallel to thesurface area of the rotatable part to which the second sealing ring isfastened.

The strip pursuant to the invention is carried in the trough of thesecond sealing ring; because its guidance task, the second sealing ringitself needs orientation or anchoring relative to the actual rotatablepart. This is achieved by a stud or the like, which is formed on aperipheral area of the cross section of the second sealing ring oppositethe trough and is laid in a somewhat complementary groove-like recess inthe relevant surface area of the rotatable part.

The fastening stud of the second sealing ring can have projections thatstand out cross-sectionally on its radially inner and/or outer surface,which increase its elasticity and permit its complete immersion in agroove-like recess in the rotatable part, on the one hand, and on theother hand guarantee it. These projections can be configured asencircling ribs, or with wavelike or sawtooth-shaped cross sections, orthe like.

The second sealing ring can also have a sealing lip that is formed on atleast one encircling surface area. If the second sealing ring consistsof a vulcanized, i.e. crosslinked (rubber) material, than it haspermanently elastic characteristics as required by a sealing lip. It istherefore obvious to provide the second sealing ring with a sealing lipalso, in order to be able to realize a double or multiple seal at lowcost.

Such a sealing lip on the second sealing ring can contact a surface areaof the opposite rotatable part. If, as the invention further foresees,the additional sealing lip on the second sealing ring lies within thecavity preferably filled with grease or similar lubricant, that isclosed off by the first sealing lip, then corrosion of the surface areaof the rotatable part cooperating with the second sealing lip isprecluded, so that damage to the second seal is avoided withoutadditional corrosion protection measures.

Alternatively and/or in addition to the additional sealing lip on thesecond sealing ring, a surface area that encircles it can be designed asthe contact surface for another sealing lip. Such a third seal can lieoutside the main seal formed by the strip pursuant to the invention andthe first sealing lip contacting it, and then protects the main sealagainst mechanical influences, for example against impacts.

A particularly simple construction is obtained when the sealing lipcontacting a contact surface of the second sealing ring is formed on thefirst sealing ring.

An arrangement has proved especially beneficial in which the back of thefirst sealing ring opposite the sealing lip contacting the strip isturned to the outside or faces the surface of the relevant ring. If itfaces the surface of the relevant ring, then it can be supported thereas the case may be, so that the sealing lip even after it is worn stillremains in tight contact with the strip. If it is turned outward, thenit can be held in shape easily with a spring element on the front of thearea carrying the sealing lip, which can then be retightened or replacedat any time because it is accessible from the outside, or can at leastbe inspected and optionally brought back into shape manually duringmaintenance. If the back of the sealing lip is covered by another partof the seal, perhaps by another section of the sealing ring itself, thenthe correct position of the sealing lip can scarcely be inspected duringmaintenance, not to mention corrected.

The invention is also distinguished by a spring element that presses asealing lip of the first sealing ring against the strip of the secondsealing ring. This can considerably increase the pressure of the sealinglip of the main seal, and with it also its sealing action.

An encircling wire or the like, for example, is suitable as a springelement. It can absorb large tensile forces that result in a far greaterradial pressure of the sealing lip than can be brought about by thesealing lip alone. To be able to fulfill its task permanently even undercorrosive environmental conditions, the spring element should becorrosion resistant, for example it should consists of stainless steelor the like. This feature can be highly important when the springelement is located outside the sealed-off area.

To avoid problems when assembling the seal, the spring element can havea somewhat circular cross section, so that unintended twisting does notimpair its uniform force action.

The spring element is preferably located on the back of the sealing lipof the first sealing element contacting the strip. From there, thepressure preferably acting radially inward can act precisely toward thefree edge of the sealing lip, so that symmetrical forces are set up inthe area of this edge and deformation of the sealing lip is reduced to aminimum.

To hold the spring element permanently in place, it should be laid in anencircling, somewhat trough-shaped recess in the first sealing element.Then it cannot slip, and the pressure action of the sealing lip issupported even after a very long time of operation. If this trough islocated outside the sealed-off area, the spring element is accessiblefrom the outside and can easily be installed after inserting the othersealing elements, and/or can be removed and/or optionally replacedand/or tightened at a later time for maintenance purposes.

For safety reasons, the invention recommends that the trough in thefirst sealing element has a circular cross section to hold the springelement, preferably along a cross-sectional peripheral angle of morethan 180°. In such a case, the spring element cannot be loosened fromthis trough even by severe vibrations.

In an arrangement of the spring element in a somewhat common plane withthe free edge of the sealing lip, the two edges of the trough holdingthe spring element lie on both sides of this plane. At least one of thetwo trough edges in the first sealing element is suitable for fasteningthe first sealing ring, by lengthening it cross-sectionally away fromthe first sealing lip. The edge area that projects backward in such acase can be provided with a stud or the like at its free end, which isused to anchor the first sealing ring in a somewhat complementarygroove-like recess in the relevant surface area of the rotatable part.The groove to hold such a stud does not have to be located on theenvelope surface of the relevant rotating part, but can also be recessedin one of its faces.

Like the fastening stud on the second sealing ring, that of the firstsealing ring can also have cross-sectionally projecting, preferablywavelike or barb-shaped elevations to increase its elasticity.

The construction pursuant to the invention undergoes furtheroptimization by the tip of the cross section of the sealing lip of thefirst sealing element contacting the strip lying somewhat on thestraight line connecting the centers of the two troughs for holding thestrip on the one hand and of the spring element on the other hand. Insuch a case, the pressure forces are transmitted in a single plane fromthe spring element over the free edge of the sealing lip to the centralarea of the strip pursuant to the invention, with no fear ofunsymmetrical deformations of the sealing lip and/or of the secondsealing ring.

It is within the scope of the invention for the sealing lip of the firstsealing element contacting the strip to have a cross section with ablunt tip. Such a blunt-angled tip is only minimally susceptible tounwanted deformations, and can therefore also withstand very highpressure forces over a period of many years and exert them on the strippursuant to the invention.

Finally, the invention is distinguished by a third sealing ring that isfastened to one of the parts that can be rotated in relation to oneanother and that has a sealing lip that contacts the other of the partsthat can be rotated in relation to one another. This sealing ring alsocan be provided with a stud or the like formed on its cross-sectionalarea opposite the sealing lip, which is used to anchor it in a somewhatcomplementary groove-like recess in the relevant surface area of therotatable part. This fastening stud can also have cross-sectionallyprojecting elevations, preferably hook-shaped or barb-like elevations.

Other features, characteristics, advantages, and actions based on theinvention are given in the following description of a preferredembodiment of the invention, with reference to the drawing. The drawingshows:

FIG. 1 a section through a ball bearing with a seal pursuant to theinvention;

FIG. 2 the seal from FIG. 1 in larger illustration; and

FIG. 3 another embodiment of the invention in an illustrationcorresponding to FIG. 2.

The ball bearing 1 in FIG. 1 consists of two concentric rings that canbe rotated in relation to one another. The outer ring 2 is shown on theleft in FIG. 1, and the inner ring 3 on the right. Fastening bores 4, 5parallel to the axis of rotation pass through both rings 2, 3. Racewaysfor at least one row of ball-shaped rollers 7 are provided in the areaof the gap 6 between the two rings 2, 3, which permit the mutualrotation of the two rings 2, 3 as a single degree of freedom of motion.With the ball bearing 1, the faces 8, 9 at the top in FIG. 1 are to beexposed to weathering. For this reason, the gap 6 between the two faces8, 9 is sealed with a seal 10 pursuant to the invention.

As shown in FIG. 2, the seal 10 consists of a first sealing ring 11 anda second sealing ring 12, each made of vulcanized material, for examplevulcanized natural or synthetic rubber. The first sealing ring 11 isfastened to the outer ring 2, and the second sealing ring 12 is fastenedto the inner ring 3. For this purpose, there is an encirclinggroove-like recess 13 in the face 1 of the outer ring 1, in which anannular extension 14 of the first sealing ring 11 engages; in the sameway, there is a likewise encircling groove-like recess 16 in theenvelope face 15 of the inner ring 3 facing the gap 6, which serves tohold an annular extension 17 on the second sealing ring 12.

The second sealing ring 12 fastened in this manner to the inner ring 3carries an annular, relatively flat trough-like recess 18 on its faceopposite the extension 17, for example with a groove-like cross section.An encircling metal strip 19 is laid in this recess, which is wrappedaround by the encircling edges of the trough 18 and is thereby preventedfrom shifting parallel to the axis of rotation of the rotary bearing 1.

There is a sealing lip 21 of the first sealing ring 11 contacting theoutside 20 of the metal strip 19 opposite the trough 18. The sealing lip21 can be formed by an edge with an obtuse open angle, for example anopen angle between 90° and 150°. For this sealing lip 21 to be pressedfirmly against the contact surface 20 of the metal strip 19 even whenthe elasticity of the sealing ring 11 declines, the sealing lip 21 ispositioned on the inside 22 of a somewhat sleeve-like section 23 of theouter sealing ring 11. The radially outer envelope surface 24 of thissleeve-like section 23, or the back 24 of the sealing ring 11 oppositethe sealing lip 21, is turned outward in the embodiment according toFIGS. 1 and 2, so that the correct position of the sealing lip 21 can beeasily inspected for the position of its back 24.

This sleeve-like section 23 at its radially outer envelope surface 24 isalso provided with an encircling trough 25 in which a metal spring 26 islaid, which is intended to press the sleeve-like section 23 and with itthe sealing lip 21 on it constantly against the metal strip 19. Thespring element 26 is preferably a tension spring, optionally with ascrew fitting to connect the two ends of the spring. Such an annularclosed tension spring can produce maximum tensile stress.

The encircling fastening extension 14 is joined to the edge 27 of thetrough 25 closest to the face 8 of the outer ring 2. For this purpose,the edge 27 of the trough 25 is bent toward the face 8. Two lateralshoulders 28, 29 opposite one another are supported on the edges of thegroove-like recess 13 in the face 8, while the extension 14 extendscompletely into this recess 13. Since the bending 30 between the edge 27of the trough 25 and the extension 14 grips the metal spring 26 inradially outer areas, it can exert a centering action on the metalspring 26 and thus also on the sealing lip 21 of the main seal 19, 21.To lay, tighten, and/or replace the metal spring 26, the trough 25,together with the back 24 of the sealing ring 11, is open toward theoutside; the trough 25 is preferably not covered by any other part ofthe sealing ring 1, so that the metal spring 26 is readily accessiblefrom the outside. To protect against corrosion, the metal spring 26should therefore be made of a stainless material.

A second sealing lip 31 is provided in the area of the upper face of thesealing ring 11 exposed to the weather, which grips around the metalstrip 19 on the outside and on top, and on the other side of it contactsthe second, inner sealing ring 12 and is intended to keep pouring rainand other effects, for example impacts, away from the main seal 19, 21.

A sealing lip 32 extending radially outward can also be provided on thesecond, inner sealing ring 12, inside, i.e. below the trough 18 for themetal strip 19, which is supported on an envelope face 33 of the outerbearing ring 2 facing the gap 6. This internal sealing lip 32, like athird sealing ring 34 that may be provided even further inward,primarily serves to hold back the lubricating grease in the gap 6.

The embodiment 10′ according to FIG. 3 differs from that of FIGS. 1 and2 only in that in this case the fastening extension 14 of the firstsealing ring 11, which engages in an encircling groove-like recess 13 inthe face 8 of the outer ring 2, is not connected to the edge 27 of thetrough 25 for the metal spring 26 closest to this face 8, but to thetrough edge 35 further away from this face 8, likewise by a bend 36.Because of this, the metal spring 26 arrives at the cavity closed off bythe main seal 19, 21, and is also removed from external influences;neither is the back 24 of the sealing lip 21 turned outward, nor does itface the surface 8 of the ring 2. In this embodiment, the metal spring26 is replaced only together with the first sealing ring 11; in theembodiment according to FIGS. 1 and 2, it could also be replacedseparately from the first sealing ring 11.

1-35. (canceled)
 36. Wind energy system comprising at least one pitchbearing (1) having two concentric rings (2, 3) rotatable relative to oneanother, each of said concentric rings having a fastening hole (4, 5)parallel to an axis of rotation, and define a gap (6) in which racewaysfor at least one row of rollers (7) are provided, and a seal (10)comprising at least one first sealing ring (11) of a permanently elasticmaterial fixed to a first (2) of the two concentric rings (2, 3) and atleast one sealing lip (21), and at least one second sealing ring (12)fixed to a second (3) of the two concentric rings (2, 3), wherein atleast the second sealing ring (12) supports a strip (19) comprised ofanother material and that extends along a peripheral portion of thesecond sealing ring and abuts the sealing lip (21) of the first sealingring (11).
 37. Wind energy system pursuant to claim 36, wherein thematerial of the second sealing ring (12) exhibits a higher specificelectrical resistance p than the strip (19).
 38. Wind energy systempursuant to claim 37, wherein the material of the second sealing ring(12) exhibits a specific electrical resistance p of more than 10³ Ωm.39. Wind energy system pursuant to claim 36, wherein the strip (19) isof metal.
 40. Wind energy system pursuant to claim 36, wherein thematerial of the strip (19) exhibits a lower coefficient of friction μthan the second sealing ring (12).
 41. Wind energy system pursuant toclaim 36, wherein a surface area (20) of the strip (19) is smooth. 42.Wind energy system pursuant to claim 41, wherein the surface area (20)of the strip (19) extends through a cylindrical envelope surface ofrotation.
 43. Wind energy system pursuant to claim 36, wherein the strip(19) comprises a closed ring.
 44. Wind energy system pursuant to claim43, wherein the strip (19) is provided with a uniform cross section. 45.Wind energy system pursuant to claim 44, wherein the strip (19) isprovided with a rectangular cross section.
 46. Wind energy systempursuant to claim 43 wherein the encircling strip (19) is fixed to thesecond sealing ring (12) and is spaced from both of the concentric rings(2, 3).
 47. Wind energy system pursuant to claim 43, wherein theencircling strip (19) is held in an encircling recess (18) in the secondsealing ring (12).
 48. Wind energy system pursuant to claim 47, whereinthe depth of the recess (18) in the second sealing ring (12) is lessthan a corresponding height of the strip (19) held therein.
 49. Windenergy system pursuant to claim 47, wherein a bottom of the recess (18)in the second sealing ring (12) is generally parallel to a surface area(15) of the concentric ring to which the second sealing ring (12) isheld.
 50. Wind energy system pursuant to claim 49, wherein a stud (17)extends from the second sealing ring (12) in a direction opposite therecess (18), to anchor the second sealing ring (12) in a complementaryrecess (16) in the surface area (15) of the second concentric ring (3).51. Wind energy system pursuant to claim 50, wherein the stud (17) isprovided with projections extending outwardly from the stud.
 52. Windenergy system pursuant to claim 36, wherein at least one sealing lip(28) is formed onto at least one encircling surface area of the firstsealing ring (11).
 53. Wind energy system pursuant to claim 36, whereinat least one sealing lip (32) of the second sealing ring (12) abuts asurface area (33) of the first concentric ring (2).
 54. Wind energysystem pursuant to claim 36, wherein at least one encircling surfacearea of the second sealing ring (12) is in contact with a surface of asealing lip (31) of the first sealing ring (11).
 55. Wind energy systempursuant to claim 54, wherein the sealing lip (31) is integral with thefirst sealing ring (11).
 56. Wind energy system pursuant to claim 36,wherein back portions of the first sealing ring (11) opposite thesealing lip (21) extend toward a surface area (8) of the concentric ring(2).
 57. Wind energy system pursuant to claim 56, and further comprisinga spring element (26) that presses the sealing lip (21) of the firstsealing ring (11) toward the strip (19) of the second sealing ring (12).58. Wind energy system pursuant to claim 57, wherein the spring element(26) is on a back portion of the sealing lip (21) of the first sealingring (11).
 59. Wind energy system pursuant to claim 57, wherein thespring element (26) comprises an encircling wire.
 60. Wind energy systempursuant to claim 57, wherein the spring element (26) is provided with acircular cross section.
 61. Wind energy system pursuant to claim 57,wherein the spring element (26) is disposed in an encircling recess (25)in the first sealing ring (11).
 62. Wind energy system pursuant to claim61, wherein the recess (25) in the first sealing ring (11) follows acircular cross section along a cross-sectional circumferential angle ofmore than 180°.
 63. Wind energy system pursuant to claim 57, wherein afirst of two trough walls (27, 35) in the first sealing ring (11) extendaway from the sealing lip (21).
 64. Wind energy system pursuant to claim63, wherein a stud (14) is formed on the first sealing ring (11) toanchor the first sealing ring (11) in a complementary recess (13) in asurface area (8) of the first concentric ring (2).
 65. Wind energysystem pursuant to claim 64, wherein the stud (14) on the first sealingring (11) is provided with projections extending therefrom.
 66. Windenergy system pursuant to claim 57, wherein a tip of the cross sectionof the sealing lip (21) of the first sealing element (11) contacting thestrip (19) lies on a generally straight line connecting centers of theencircling recesses (18, 25).
 67. Wind energy system pursuant to claim36, wherein the sealing lip (21) of the first sealing ring (11) isprovided with a cross section with an obtuse-angled tip.
 68. Wind energysystem pursuant to claim 36, wherein a third sealing ring (34) isfastened to one of the concentric rings (2, 3), and has a sealing lipthat contacts the other of the two concentric rings (2, 3).
 69. Windenergy system pursuant to claim 68, wherein the third sealing ring (34)is provided with a stud extending from the sealing lip, to anchor thethird sealing ring in a complementary recess in a surface of the secondsealing ring.
 70. Wind energy system pursuant to claim 69, wherein thestud on the third sealing ring (34) is provided with projectionsextending outwardly therefrom.